FIELD OF THE INVENTION
The present invention relates to a grip-type cutter knife wherein a knife blade is projected from a cutter body thereof by pressing a trigger lever.
FIGS. 1 and 2 show one example of a well-known conventional grip-type cutter knife 10. This cutter knife comprises an elongated cutter body 11 provided with a grip portion 12. At the front end of the body 11, there is provided a circular rotary blade 15. In FIG. 1, the rotary blade 15 is projected from the body for cutting. In FIG. 2, the rotary blade 15 is retracted in the body, and the cutting is impossible.
The rotary blade 15 is connected to a swing member which is pivotally supported in the cutter body 11. A part of this swing member is projected from the grip portion 12 to serve as a trigger lever 14 (FIG. 2). The swing member is forced into the non-cutting position (FIG. 2) by a spring member (not shown) arranged in the cutter body 11. That is, when grasping the trigger lever 14 into the cutter body 11 against the spring force, the rotary blade 15 is projected from the forward end of the cutter body 11 (FIG. 1). On the other hand, when releasing the grasping hand, the rotary blade 15 is retracted into a platform 13 at the forward end of the cutter body 11.
Among the grip-type cutters, there are some products which have a cover on the platform 13 of the cutter body 11, or which have a locking mechanism prohibiting the swing of the swing member, in order to avoid the unintentional projection of the blade. The cutter having the locking mechanism is more convenient in handling than that having the cover.
Even among the grip-type cutters having a locking mechanism, although a mechanism locking the knife blade in retracted position is known, a mechanism locking the knife blade in projected position is unknown. It is understood from FIG. 1 that, in order to keep the knife blade projected, a user must keep on grasping the grip portion 12 against the spring force to press the trigger lever in. This would bring physical fatigue to the user in continuous working.